Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment, as examples. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductive layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon.
Capacitors are elements that are used extensively in semiconductor devices for storing an electrical charge. Capacitors essentially comprise two conductive plates separated by an insulating or dielectric material. Capacitors are used in applications such as electronic filters, analog-to-digital converters, memory devices, control applications, and many other types of semiconductor device applications.
In some semiconductor devices, power lines and ground lines are routed to logic gates and other devices in integrated circuits. The current from a power supply flows through the power lines, logic gates, and finally to ground. During switching of the logic gates, a large amount of change in the current occurs within a short period of time. Decoupling capacitors are used to absorb these glitches during current switching. Decoupling capacitors are also used to maintain a constant voltage between the supply voltage and ground. The decoupling capacitors act as charge reservoirs that additionally supply current to circuits when required, to prevent momentary drops in the supplied voltage.
One type of decoupling capacitor used is referred to as a metal-insulator-metal (MIM) capacitor. A MIM capacitor has two metal layers and a dielectric insulator layer between the two metal layers. A capacitance is formed between the two metal layers. MIM capacitors are often fabricated in interconnect layers of a semiconductor device.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.